JP2003534894A - Method and apparatus for performing a cleanliness inspection of a final gearbox assembly - Google Patents

Abstract

(57) Abstract: A cleanness test of a gear box (12) is performed by flowing an oily fluid through a gear box (12) and then through a filter (20). The filter (20) is then weighed to determine the weight of contaminants trapped in the filter. The contaminant weight is compared to a predetermined level, and if the contaminant weight is below the predetermined level, the gearbox (12) is considered to be acceptable. The method includes an apparatus including a source of oily fluid (18) in fluid communication with an inlet (14) of a gearbox (12) and a filter (20) in fluid communication with an outlet (16) of the gearbox (12). This is performed in (10). A device such as a pump (24) is provided to allow oily fluid to flow through the gearbox (12) and the filter (20).

Description

Detailed Description of the Invention

Statement on Federally Sponsored Research and Development [0001] Contract No. N000019-96-C-0080 awarded by the Department of the Navy
The US Government may have certain rights in this invention.

[0002]

TECHNICAL FIELD OF THE INVENTION

The present invention relates generally to gearboxes, and more specifically to cleanliness inspection of enclosed gearboxes used in gas turbine engines.

[0003]

[Prior art]

Gas turbine engines used to propel aircraft in flight include a compressor that supplies pressurized air to a combustor, where the air is mixed with fuel and ignited to produce hot combustion gases. These gases flow downstream to one or more turbines to extract energy from the gases, power the compressor via a shaft, and generate propulsion to propel the aircraft.

Aircraft engines typically include many accessory devices such as fuel pumps, lubricant pumps, generators and control units, which are driven by the core engine.
This is typically done by an accessory drive train that includes an inlet gearbox, a radial drive shaft, a transmission gearbox, a horizontal drive shaft, and an accessory gearbox. During manufacture and assembly, the gearbox can become contaminated with metal debris such as steel shotpeen debris. When such a contaminated gearbox is installed in an engine, contaminants can be transferred to other engine components such as bearings by the engine's lubrication system. Therefore, it is important that the gearbox attached to the engine is free of contaminants to eliminate the possibility of bearing or other component failure.

Efforts to produce a contaminant-free gearbox generally include cleaning the single gearbox component and performing a cleanliness inspection step prior to final assembly. Conventionally, cleanliness inspection of such parts uses alcohol-based fluids to remove any contaminants that may be present on the part. Such efforts are not always successful enough, as additional contamination can occur during final assembly. Therefore, it may be helpful to perform a gearbox cleanliness check after final assembly. However, some gearboxes, especially auxiliary gearboxes, are "closed gearboxes" in that they are completely closed to the external environment. Performing a final assembly cleanliness test of a closed gearbox with a standard alcohol-based fluid creates a dry spot inside the gearbox, which results in gearbox corrosion.

[0006]

[Problems to be Solved by the Invention]

Therefore, there is a need for an apparatus and method for performing a cleanliness inspection of closed gearboxes after final assembly that does not produce internal dry spots.

[0007]

[Means for Solving the Problems]

The above requirements are met by the present invention, which provides a method for performing a cleanliness check of a gearbox, in which an oily fluid is passed through the gearbox and then through a filter. The filter is then weighed and the weight of contaminant collected in the filter is determined. The weight of pollutants is compared to a predetermined level,
The gearbox is acceptable if the contaminant weight is below a predetermined level. The method is performed in an apparatus that includes a source of oily fluid in fluid communication with the inlet of the gearbox and a filter in fluid communication with the outlet of the gearbox. A device such as a pump is provided to force the oily fluid through the gearbox and filter.

The invention and its advantages over the prior art will become apparent upon reading the following detailed description and the appended claims with reference to the accompanying drawings.

The subject matter regarded as the invention is particularly pointed out and distinctly claimed in the introductory part of the specification. The present invention, however, may best be understood by reference to the following description taken in connection with the figures of the accompanying drawings.

[0010]

DETAILED DESCRIPTION OF THE INVENTION

In the drawings, the same reference numbers represent the same elements throughout the various figures,
With reference to that figure, an apparatus 10 for performing a cleanliness test of a final assembled hermetic gearbox 12 is shown schematically in FIG. The gear box 12
It may be any type of gearbox, such as a gas turbine engine accessory gearbox that is hermetically sealed to its external environment. Since the gearbox generally needs to be lubricated during operation, the gearbox 12 includes a conventional lubricating oil inlet 14 for introducing lubricating oil into the gearbox 12 and lubricating oil.
Includes a conventional lube oil outlet 16 for exiting.

The apparatus 10 further includes a cleanliness test fluid source 18, a prefilter 19, and a main filter 20. The cleanliness test fluid supply 18 is in fluid communication with a preliminary filter 19, which in turn is in fluid communication with the lubricating oil inlet 14. Main filter 2
0 is in fluid communication with the lubricating oil outlet 16. Specifically, each element is connected by a plurality of suitable fluid conduits 22. A pump 24 or similar means is provided to allow cleanliness test fluid from source 18 to flow through prefilter 19, gearbox 12, and then main filter 20. Cleanliness inspection fluid is gearbox 1
As it flows through 2, the cleanliness test fluid entrains contaminants that are internal to the gearbox 12. The contaminants entrained in the cleanliness test fluid are then trapped therein as the fluid passes through the main filter 20. The fluid exiting the main filter 20 is directed to a fluid collector or reservoir 26 via another fluid conduit 22. The prefilter 19 ensures that the cleanliness test fluid is contaminant-free before passing through the gearbox 12.

The weight of contaminants removed from the gearbox 12 is determined by weighing the main filter 20 and then comparing the weight of the main filter 20 after flowing the fluid with the filter weight before flowing the fluid. . This weight difference will therefore be equal to the weight of contaminants trapped in the main filter 20. Although pump 24 is shown in FIG. 1 as being installed between cleanliness test fluid source 18 and gearbox 12, pump 24 could instead be installed downstream of gearbox 12. Please note that. The device 10 also includes a gearbox 12 during fluid flow operations.
Includes a suitable jig (not shown) for holding the.

In one preferred embodiment of the present invention, the cleanliness test fluid is an oily fluid. By using an oleaginous fluid, the present invention eliminates internal dry spots that tend to occur when using conventional alcohol-based cleanliness test fluids in enclosed gearboxes. The oily fluid should be of suitable viscosity so that it is well flowing, unclogging, and entrains most of the contaminant particles in the gearbox. One particular oily fluid found to perform well is M
IL-L-23699 oil. The fluid conduit 22 is made of a material that does not fail when lined with nylon or with MIL-L-23699 oil.

Both the preliminary and main filters 19 and 20 are preferably 3 micron collection filters. Therefore, filters 19 and 20 will trap contaminant particles of 3 microns or larger in size. Filters 19 and 20 should both be large enough to handle the amount of cleanliness test fluid flowing therethrough, which is described in more detail below.

During operation of the device 10, the main filter 20 will trap some amount of oily fluid in addition to the contaminants it is intended to trap. When the main filter 20 is weighed after flowing the fluid, any residual fluid remaining in the main filter 20 will be included in the weight difference. An auxiliary device 28 is used in conjunction with the main device 10 to remove such residual cleanliness test fluid and thereby eliminate its effect on determining the contaminant weight. The two devices 10 and 28 combine to form the overall device of the present invention. As shown schematically in FIG. 2, the auxiliary device 28 includes a tank 30 containing a solvent 32. The tank 30 is large enough to receive the main filter 20 therein. Therefore, the main filter 20 can be immersed in the solvent 32. The solvent 32 dissolves the oily fluid trapped in the main filter 20. Illustrative solvents suitable for use in the present invention include mineral spirits and isopropyl alcohol (or combinations thereof).

The dipping process removes residual oil from the main filter 20 while leaving contaminants entirely behind. However, some contaminants may be removed from the main filter 20 along with the dissolved oily fluid. To recapture these contaminant particles, the auxiliary device 28 further includes a second filter 34 in fluid communication with an outlet 36 formed in the tank 30. The second filter 34 is also preferably a 3 micron collection filter. Another pump 38 or similar means is provided to flush the solvent 32 from the tank 30 through the second filter 34, which recaptures contaminants entrained in the solvent 32. The fluid flowing out of the second filter 34 is guided to the solvent recovery device or reservoir 40. As in main device 10, all of the elements of auxiliary device 28 are in fluid communication by a plurality of suitable fluid conduits 42. The total weight of contaminants removed from the gearbox 12 is then weighed on both filters 20 and 34 and the combined filter weight is used to determine the total weight of filter 2 prior to use.
Determined by comparing to the combined weight of 0 and 34.

Referring now to FIG. 3, one preferred embodiment for using the devices 10 and 28 described above to perform a cleanliness test of the finally assembled hermetic gearbox 12 is shown.
be written. The method begins at block 100 with a flow of oily fluid through gearbox 12 (to entrain contaminants in gearbox 12) and then through main filter 20 (to trap entrained contaminants). 10
Go to 2. The fluid must be supplied in sufficient quantity and at sufficient pressure to completely wash out contaminants from the gearbox 12. If the fluid volume and pressure are too small, not all of the contaminants will be entrained. If the fluid volume and / or pressure is too great, the main filter 20 may be damaged. In one preferred configuration, about 50 gallons of oily fluid is flowed through gearbox 12 at about 40 pounds per square inch.

The method then proceeds to block 104, where the main filter 20 is removed from the apparatus 10 in a solvent 32 in the tank 30 to dissolve residual oily fluid trapped in the main filter 20. Placed in. Next, at block 106, the spent solvent 32 is passed through a second filter 34 to re-entrap any contaminants that may have been removed from the main filter 20 along with the dissolved oily fluid during the solvent dipping step. To do. In one preferred embodiment, blocks 104 and 106 are each performed twice. Specifically, the main filter 20 is first immersed in about 300 milliliters of mineral spirits for about 30 minutes, and then subsequently immersed in about 300 milliliters of isopropyl alcohol for about 30 minutes. Both of these solvents are passed through the second filter 34. This combination of solvents has been found to be very effective in dissolving oily fluids.

Once these steps are complete, both filters 20 and 34 are weighed to determine the cumulative weight of contaminants trapped within filters 20 and 34, as shown in block 108. Specifically, the two filters 20 and 34 are weighed, and then the total weight of the filters 20 and 34 before use is the total weight of the filters 20 and 34 after use to obtain the net weight of the trapped contaminants. Deducted from the weight.

The method then proceeds to block 110, where the net contaminant weight is compared to a predetermined level to determine the effectiveness of the cleanliness test. If the net contaminant weight is below a predetermined level, then the method proceeds to block 11
Proceeding to 2, where the gearbox 12 is accepted as having passed the cleanliness check, the method then completes as indicated at block 114. However,
If, at block 110, the net pollutant weight exceeds a predetermined level, this indicates that the gearbox 12 is currently unacceptable and the method proceeds to block 116. At block 116, the number of times gearbox 12 has been subjected to flowing fluid is considered. If the gearbox has undergone relatively few attempts to flush away contaminants, the method repeats the sequence of flushing and dipping to try to achieve the net contaminant weight limit. Then, the process returns to block 102.

If the gearbox has already undergone numerous attempts, and if the net contaminant weight is still above a predetermined level, then there is no chance that further flushing will be successful. Generally, a few or more attempts are considered excessive. At this point, the method proceeds to block 118, where the gearbox 12 is rejected as having failed the cleanliness check, and the cleanliness check method is complete, as shown at block 114. Generally, the rejected gearbox is then disassembled and inspected. The gearbox will be reassembled with parts replaced as needed. The reassembled gearbox will then undergo the cleanliness inspection method starting at block 100.

A predetermined level below which the net contaminant weight is considered acceptable must be determined for each gearbox based primarily on the size of the gearbox. The predetermined level is set to a level at which it can be reasonably assured that the large contaminant particles that most damage the gearbox or other parts have been removed. Generally, the predetermined level is 70-
It will be in the 90 milligram range.

The above describes an apparatus and method for performing a cleanliness test of a final assembled hermetic gearbox that does not produce internal dry spots. While particular embodiments of the present invention have been described, various modifications to the invention can be made without departing from the spirit and scope of the invention as set forth in the appended claims. It will be apparent to those skilled in the art that

[Brief description of drawings]

FIG. 1 is a schematic diagram of an apparatus for performing a final assembly cleanliness inspection of a sealed gearbox.

2 is a schematic view of an auxiliary device for use with the device of FIG.

FIG. 3 is a flow chart illustrating a method of performing a final assembly cleanliness inspection of a sealed gearbox.

[Explanation of symbols]

  10 devices   12 gearbox   14 Gearbox entrance   16 Gearbox outlet   18 Cleanliness inspection fluid supply source   19 Second filter (preliminary filter)   20 main filters   22 Fluid conduit   24 pumps   26 Reservoir

─────────────────────────────────────────────────── ─── Continued front page    (81) Designated countries EP (AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, I T, LU, MC, NL, PT, SE, TR), JP F term (reference) 3B201 AA47 BB01 BB62 BB95 CA05                       CC21

Claims (30)

[Claims] 1. A method of performing a cleanliness test of a gearbox (12), comprising: (a) flowing an oily fluid through the gearbox (12) and then through a filter (20); Weighing the filter (20) and determining the weight of the contaminant collected in the filter (20), (c) comparing the weight of the contaminant to a predetermined level, and If the weight is below the predetermined level, the gearbox (12) is acceptable. 2. The method of claim 1 further comprising the step of immersing the filter (20) in a solvent (32) prior to the step of metering the filter. 3. The method of claim 2, wherein the step of immersing the filter in a solvent (32) comprises immersing the filter (20) for about 30 minutes or more. Method. 4. The filter (20) is immersed in a first solvent (32) prior to the step of weighing the filter (20) and then the filter (20).
The method of claim 1, further comprising immersing the in a second solvent (32). 5. The first solvent (32) is mineral spirits, and the second solvent (32) is isopropyl alcohol.
The method described in. 6. The method of claim 1, further comprising flowing the oily fluid through another filter (19) prior to flowing the oily fluid through the gearbox (12). . 7. The method of claim 1, wherein the filter (20) is a 3 micron collection filter. 8. The method of claim 1, wherein the oily fluid is MIL-L-23699 oil. 9. The step of flowing an oily fluid through the gearbox (12) and then the filter (20) flows about 50 gallons of the oily fluid through the gearbox (12) at about 40 pounds per square inch. The method of claim 1, comprising: 10. The method of claim 1, wherein steps (a) through (c) are repeated if the weight of the contaminant exceeds the predetermined level. Method. 11. Method according to claim 1, characterized in that the gearbox (12) is a final assembled closed gearbox (12). 12. A method of performing a cleanliness test of a finally assembled hermetically sealed gearbox (12), comprising: (a) passing through the gearbox (12) and then a first filter (20). Flowing, (b) immersing the first filter (20) in a solvent (32), (c) passing the solvent (32) through a second filter (34), (d) The first and second filters (20, 34) are weighed and the first and second filters are measured.
Determining the weight of the contaminant collected in the filter, (e) comparing the weight of the contaminant to a predetermined level, and if the weight of the contaminant is below the predetermined level, Said gearbox (12) being permissible. 13. The step of soaking the filter (20) in a solvent (32) comprises soaking the filter (20) for about 30 minutes or more. The method described in. 14. The first filter (20) is provided with a solvent (32) as described above.
) Subsequent to the step of immersing the first filter (20) in the second solvent (3
13. The method of claim 12, further comprising: dipping in 2) and passing the second solvent (32) through the second filter (34). 15. Process according to claim 14, characterized in that the first mentioned solvent (32) is mineral spirits and the second solvent (32) is isopropyl alcohol. 16. The method of claim 12, wherein the first and second filters (20, 34) are 3 micron collection filters. 17. The method of claim 12, wherein the oily fluid is MIL-L-23699 oil. 18. The gearbox (12) and then the filter (20).
13. The method of claim 12, wherein said step of flowing an oily fluid through comprises flowing about 50 gallons of said oily fluid through said gearbox (12) at about 40 pounds per square inch. 19. The method of claim 12, further comprising flowing the oily fluid through another filter (19) prior to flowing the oily fluid through the gearbox (12). . 20. The steps of (a) to (c) are repeated if the weight of the contaminant exceeds the predetermined level. Method. 21. A gearbox (1) having an inlet (14) and an outlet (16).
A device (10) for performing the cleanliness test of 2), comprising a fluid source (18) in fluid communication with the gearbox inlet (14) and a fluid at the gearbox outlet (16). A device (10) comprising a filter (20) in communication and means for flowing the oily fluid through the gearbox (12) and the filter (20). 22. The device (10) of claim 21, wherein the means for flowing the oily fluid through the gearbox (12) and the filter (20) is a pump (24). . 23. The device (10) of claim 21, wherein the filter (20) is a 3 micron collection filter. 24. The device (10) of claim 21, wherein the oily fluid is MIL-L-23699 oil. 25. The device (10) of claim 21, further comprising means for immersing the filter (20) in a solvent (32). 26. Device (10) according to claim 25, characterized in that the solvent (32) is mineral spirits. 27. The device (10) of claim 25, wherein the solvent (32) is isopropyl alcohol. 28. The device (10) of claim 25, further comprising a second filter (34) for passing the solvent (32). 29. The source of oily fluid (18) and the gearbox inlet (
22. The device (10) of claim 21, further comprising a second filter (19) in fluid communication between 14). 30. The device (10) of claim 29, wherein the second filter (19) is a 3 micron collection filter.